Tendon vs Ligament: What’s the Difference (and What’s “Sinew,” Anyway?)

Written by Dr Ilma Imtiaz

You probably don’t think much about your tendons and ligaments when you’re walking the dog, lifting weights, climbing stairs or heading out for a weekend hike. But behind almost every movement is an intricate network of collagen-rich tissues quietly transferring force, guiding your joints and helping keep your body moving. And in midlife, these tissues can suddenly seem a little more noticeable.

Perhaps your Achilles feels less forgiving after a long walk, your knees need a little more warming up before a workout, or your body simply seems to appreciate recovery days more than it once did. Tendon and ligament problems are also far from uncommon, with around 17 million tendon and ligament injuries estimated to occur each year in the United States alone [1].

So, what exactly is the difference between a tendon and a ligament, how do they support the way we move, and where does sinew fit into the picture?

Tendon vs ligament: the simple difference

The easiest way to remember the difference is: tendons connect muscle to bone whilst ligaments connect bone to bone [2].

Think about rising onto your toes. Your calf muscles contract, but they don't directly pull your heel upward. The force travels through your Achilles tendon, which connects those muscles to your heel bone.

Now imagine stepping awkwardly off a curb. The ligaments surrounding your ankle help guide the joint and limit excessive movement. In simple terms, tendons help transmit movement; ligaments help keep that movement controlled.

What exactly does a tendon do?

Tendons are strong, rope-like tissues that connect muscle to bone, transferring the force created by your muscles to help you move. Some familiar examples include the Achilles, patellar, rotator cuff and biceps tendons [3]. But tendons aren't simply biological ropes. Some can store and release elastic energy. During walking and running, for example, the Achilles tendon acts somewhat like a spring, stretching under load and returning some of that energy as you move forward. Tendons are rich in type I collagen, with fibres largely arranged along the direction of pull, giving them considerable tensile strength. 

Tendons adapt to the forces we regularly place on them. That is one reason progressive loading is so valuable [4]. When a tendon is exposed to repeated, manageable amounts of mechanical load, it can gradually remodel and adapt to meet those demands. But this process takes time. That’s where gradual progression matters. Slowly increasing the amount of walking, running, jumping or resistance training you do gives your tendons time to adjust as the demands on them increase. A sudden jump, doubling your running distance or adding several high-impact classes in one week, can increase the load much faster than the tissue has had time to adapt.

And there’s another reason pacing matters: your muscles and tendons don’t necessarily adapt at the same rate. Your muscles may feel ready to lift heavier, run farther or train more often before your tendons have fully caught up.

What do ligaments do?

Ligaments are also strong, collagen-rich tissues, but instead of connecting muscle to bone, they connect bone to bone across a joint. Their job is less about generating movement and more about helping guide it. Ligaments contribute to joint stability, help maintain alignment and limit excessive movement in particular directions. Examples include the ACL and MCL at the knee, lateral ankle ligaments and ligaments of the spine [5]. Their fiber arrangement, however, can be more varied because ligaments often need to manage forces arriving from several directions around a joint. It is a beautifully practical example of how structure follows function in the human body.

So, what is a “sinew”?

Here's one for your next trivia night. Sinew isn't a separate anatomical structure. It is an older English word most commonly used to describe a tendon, the tough cord of tissue connecting muscle to bone [6]. Historically, the word was used more broadly for strong, fibrous tissues in the body, which is why you may still hear expressions such as “the sinews of the body” or someone saying they have “pulled a sinew.”

Modern anatomy is much more specific. A healthcare professional is more likely to identify whether the structure involved is a tendon, ligament, muscle, fascia or another tissue. “Sinew” has even acquired a figurative meaning over time, describing strength or something that provides essential support.

What tendons and ligaments have in common: collagen

Despite their different jobs, both are rich in type I collagen, which provides much of their tensile strength. They also adapt more slowly than muscle, partly because of relatively limited blood supply, low cellularity and slow collagen turnover. It’s another reason consistent, progressive loading matters: connective tissues need time to respond.

Strain or sprain: what's the difference?

Here's an easy distinction to remember: a strain usually involves a muscle or tendon, while a sprain involves a ligament.

Pain alone can't always tell you which tissue is involved; always seek professional assessment for a significant injury, swelling, instability, loss of function, or symptoms that persist or worsen.

Why tendons and ligaments deserve more attention in midlife

If your body seems to appreciate a little more preparation and recovery than it did a decade ago, you're not alone. Muscle and joint discomfort are commonly reported during the menopause transition. But midlife musculoskeletal health is complex. Previous injuries, sleep, stress, activity levels, muscle strength, body composition, nutrition, aging and hormone-related changes may all contribute.

That doesn't mean every new ache is caused by menopause. And it certainly doesn't mean becoming less active. In fact, this stage of life can be an excellent time to become more intentional about building physical capacity. Progressive resistance training, regular walking, balance work and appropriately progressed impact exercise can all form part of an active midlife routine. The important word is progressive [4,7].

Connective tissues respond to mechanical loading, but adaptation takes time. Rather than asking, “How can I make my tendons stronger as quickly as possible?”, a more useful question may be: “Am I giving my body a manageable and repeatable combination of loading, nutrition and recovery?” That's a much more sustainable way to think about staying active through your 40s, 50s and beyond.

How can you support healthy tendons and ligaments?

There isn't one magic exercise, food or supplement for connective tissue.

The foundations matter most:

• Build activity gradually. Give your body time to adapt when increasing walking, running, hills, jumping or resistance training.
• Prioritize strength. Exercises such as calf raises, squats, rows and presses can progressively load muscles and their associated connective tissues when appropriate for your abilities.
• Respect recovery. Rest and lighter days are part of adaptation, particularly when you're beginning a new program or returning after a break.
• Eat enough protein. Collagen doesn't exist in isolation from the rest of your nutrition. Adequate dietary protein supports the body's normal tissue-building processes.
• Include vitamin C-rich foods. Vitamin C contributes to normal collagen formation.
• Be consistent. Connective tissues adapt over time, making a repeatable routine more useful than occasional bursts of intense activity.
• Consider targeted collagen peptides as a complementary part of your nutrition and movement routine.
• That last point is worth exploring because not all collagen peptides have been studied for the same purpose.

Where do collagen peptides fit?

Now that we know tendons and ligaments are largely built around collagen, there’s an obvious question: can nutrition support these tissues too? Specific collagen peptides have been studied alongside exercise as one way to provide additional nutritional support for healthy connective tissue. One of these is Tendoforte®, the bioactive collagen peptide used in Sparkle Wellness formulas for tendon and ligament support. And the research gives us an interesting glimpse into how adaptable tendons really are.

What does the research tell us about supporting tendon adaptation?

We’ve seen that tendons are living tissues that respond to the forces we place on them. Research suggests specific collagen peptides may provide additional nutritional support for that adaptation alongside exercise. In a 14-week study, healthy men combined resistance training with either 5 g of Tendoforte® or placebo daily. Achilles tendon cross-sectional area increased by 11.0% with Tendoforte® compared with 4.7% with training alone [8]. A second 14-week study found greater increases in specific regions of the patellar tendon with Tendoforte® plus resistance training compared with training alone [9].

The practical takeaway? Movement provides the stimulus, while targeted nutrition can provide support. And movement is never the work of one tissue alone. When you walk, hike or squat, muscles generate force, tendons transfer it, ligaments help guide your joints, cartilage supports smooth movement and bones provide structure. That’s why collagen support can be targeted or take a broader approach. 

1. Tendoforte® provides targeted nutritional support for healthy tendons and ligaments alongside an active lifestyle.
2. Advanced 4-in-1 Boost combines four specific Bioactive Collagen Peptides®: 

• Tendoforte® — for tendons and ligaments
• Fortigel® — for joints and cartilage
• Fortibone® — for bone
• Verisol® — for skin

Different tissues, different areas of research, but one bigger picture: supporting an active body through midlife and beyond.

The Take Home Message

Tendons connect muscle to bone and help transfer force. Ligaments connect bone to bone and help guide and stabilize our joints. And sinew? That's simply an older word usually referring to a tendon. But perhaps the more interesting lesson is what these tissues have in common.

They're collagen-rich, living tissues that respond to how we use them. And because that adaptation happens gradually, supporting them isn't about doing less as you get older. It's about giving your body the right combination of progressive movement, strength, nutrition and recovery. Your muscles may get most of the attention, but the tissues quietly connecting everything together deserve some love too.

Dr. Ilma Imtiaz has a background in biomedical and naturopathic research and recently completed her PhD at the National Centre for Naturopathic Medicine, Southern Cross University, Australia. She is a lead and co-author of multiple peer-reviewed publications, including experimental and review papers across herbal medicine, cancer biology and molecular mechanisms.

At the heart of her work is a passion for science communication, translating complex evidence into clear, engaging, and accessible insights. She is committed to evidence-led wellness and supporting informed, balanced health decisions.

References

1. Romano F, Lopresti F, Di Gesù R, La Carrubba V. Tissue engineering for tendon and ligament repair: insights and advances. VIEW. 2025;6:20250063. https://doi.org/10.1002/VIW.20250063 
2. Bobzin L, Roberts RR, Chen HJ, Crump JG, Merrill AE. Development and maintenance of tendons and ligaments. Development. 2021;148(8):dev186916. https://doi.org/10.1242/dev.186916
3. Weinreb JH, Sheth C, Apostolakos J, et al. Tendon structure, disease, and imaging. Muscles Ligaments Tendons J. 2014;4(1):66-73. 
4. Breda SJ, Oei EHG, Zwerver J, et al. Effectiveness of progressive tendon-loading exercise therapy in patients with patellar tendinopathy: a randomised clinical trial. Br J Sports Med. 2021;55(9):501-509. https://doi.org/10.1136/bjsports-2020-103403 
5. Tham SC, Tsou IYY, Chee TSG. Knee and ankle ligaments: magnetic resonance imaging findings of normal anatomy and at injury. Ann Acad Med Singap. 2008;37(4):324-329. 
6. Baar K. Minimizing injury and maximizing return to play: lessons from engineered ligaments. Sports Med. 2017;47(suppl 1):5-11. https://doi.org/10.1007/s40279-017-0719-x 
7. Ansari M, Hussain F, Shopon M, Ajmal H, Asif M, David S. Hormonal shifts and structural strain: a literature review of menopause and perimenopause in relation to overuse injuries and stress fractures. Ann Rehabil Med. 2026;50(3):139-149. https://doi.org/10.5535/arm.250134
8. Jerger S, Centner C, Lauber B, et al. Effects of specific collagen peptide supplementation combined with resistance training on Achilles tendon properties. Scand J Med Sci Sports. 2022;32(7):1131-1141. https://doi.org/10.1111/sms.14164 
9. Jerger S, Centner C, Lauber B, et al. Specific collagen peptides increase adaptions of patellar tendon morphology following 14-weeks of high-load resistance training: a randomized-controlled trial. Eur J Sport Sci. 2023;23(12):2329-2339. https://doi.org/10.1080/17461391.2023.2232758

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